Method of manufacture of a coated valving member

ABSTRACT

All areas of the butterfly-type valving member which may be exposed to attack by corrosive substances, are coated with a protective material of the class of tetrafluoroethylene or equivalent substance, by a high-pressure and high-temperature molding process; the process involving withdrawing support from a journal end of the valve member during a critical phase of the molding procedure to ensure adequate coating of said journal end including the customary turning center hole thereof.

United States Patent Walchle et al.

[ 1 I June 13, 1972 [54] METHOD OF MANUFACTURE OF A COATED VALVING MEMBER [72] Inventors: David L. Walchle; Peter J. Schmidt, both of Cincinnati, Ohio [73] Assignee: Xomox Corporation, Cincinnati, Ohio [22] Filed: July 16, 1970 [21] App1.No.: 55,370

[56] References Cited UNITED STATES PATENTS 2,361,348 10/1944 Dickson et a1 ..267/278 3 146,286 8/1964 Freed ..264/ 274 3,336,938 8/1967 Schenck 137/375 3,394,914 7/1968 Nagasato 1 37/375 X 3,450,151 6/1969 Heutzenroeder. 137/375 3,508,573 4/1970 Smith ...l37/375 2,059,687 11/1936 Gagg ..25 1/286 Primary Examiner-Henry T. Klinksiek Attorney-J. Warren Kinney, Jr.

[57] ABSTRACT All areas of the butterfly-type valving member which may be exposed to attack by corrosive substances, are coated with a protective material of the class of tetrafluoroethylene or equivalent substance, by a high-pressure and high-temperature molding process; the process involving withdrawing support from a journal end of the valve member during a critical phase of the molding procedure to ensure adequate coating of said journal end including the customary turning center hole thereof.

13 Claims, 10 Drawing Figures 2,534,947 12/1950 Bright ..264/274 X 2,923,523 2/1960 Taylor... .....251/306 X PATENTEBJUN 1a 1972 SHEET 10F Q FIG-3 m/vE/vroRs DAVID L. WALCHLE PETER J. SCHMIDT er 42 Arr-0 5 P'AT'ENTEDJun 13 m2 3. 670.071 sum 2 or 5 FIG-5 19 INVENTORS DAVID L. WALCHLE PETER J. SCHMIDT ATTO PATENTEDJUM 13 m2 SHEET 3 OF 3 H NOW EL VAS ww N QE METHOD OF MANUFACTURE OF A COATED VALVING MEMBER This invention relates to a coated valving member and method of manufacturing the same.

The valving member here concerned involves a butterfly valve or paddle valve, which usually comprises a substantially flat circular body plate or disc of metal or other rigid material, having located at opposite ends of a diameter or chord a pair of axially aligned cylindrical shaft sections. The shaft sections may be welded, brazed, or otherwise fixedly secured to the body plate, with the shaft section axes disposed in substantially the mean plane of the body plate. The assembly may be constructed of a corrosion-resistant material, preferably a metal of the class of stainless steel, brass or bronze. If desired, the assembly may be cast or molded as one piece.

In accordance with the present invention, the valving member is to be coated with a tough corrosion-resistant and wear-resistant material having a low coefficient of friction and inherent self-lubricating, impervious properties. The coating material may be a moldable plastic of the class of Teflon TFE (tetrafluoroethylene), or other high density polyethylene, polycarbonate or polypropylene, and including such products as Teflon F EP, Kynar, Kel-F, Penton and the like.

The coating process involves high-pressure, high-temperature application of the coating to the body plate and to both shaft sections, with particular attention given to fully enveloping at least one of the shaft sections. The coating is applied by injection molding procedure, and involves supporting the bar valving member in a mold in such manner as will permit a flow of coating material uniformly onto all surfaces of the body plate and its shaft sections, including the terminal end of one of said sections. For this purpose, a novel procedure and technique are resorted to, as one object of the present invention.

The coated valving member after removal from the mold, may be mounted in a butterfly valve body which also may be plastic coated and lined, the valve body having aligned bearings to receive and rotatably support the shaft sections of the valving member. One shaft section of the valving member may be disposed for manipulation, manually or mechanically, for selective disposition of the valving member to open or closed positions within the valve body.

An object of the present invention is to provide an improved coated valving member for butterfly valves, and a highly effective and desirable method of producing such a valving member.

Another object of the invention is to minimize the cost of producing a plastic coated valving member by eliminating most or all machining of the valving member components.

Another object is to provide an improved coating process for valving members which is highly efficient, and productive of a minimum number of rejects in the manufacture, the coating being fully protective of all areas of the valving member which might be exposed to corrosive chemicals or gases in service.

A further object of the invention is to provide a novel method and means of coating, whereby a shaft terminal end of the valving member may be effectively and completely coated during the coating operation, with the assurance of maintaining uniformity of coating thickness in other areas of the valving member.

Another object is to provide a valving member of the character stated, which upon incorporation in a lined valve body, ensures easy manipulation of the valve and minimizes the likelihood of leakage of any fluid from the interior of the valve while in service.

The foregoing and other objects are attained by the means described herein and illustrated upon the accompanying drawings, in which:

FIG. 1 is a perspective view of a butterfly-type valving member such as the present invention is concerned with, said valving member being uncoated.

FIG. 2 is a view of the valving member with the plastic coating applied thereto.

FIG. 3 is a cross section of a mold in which is supported the valving member of FIG. 1 preparatory to injection of fluidic plastic into the mold and about the valving member.

FIG. 4 is a view similar to FIG. 3, showing the mold charged with plastic coating material just prior to solidification of the material.

FIG. 5 is a view similar to FIG. 4, showing a phase of the molding process wherein a mandrel supportive of the valving member within the mold has been retracted, to permit flow of coating material into an end cavity of the valving member shaft, while partially solidified coating material supports the valving member within the mold.

FIG. 6 is a cross-sectional view taken on line 6-6 of FIG. 5.

FIG. 7 is an edge view of the completed valving member.

FIG. 8 is a face view of the same.

FIG. 9 is a fragmental cross section taken on line 9-9 of FIG. 8.

FIG. 10 is a fragmental cross section taken on line 10-10 of FIG. 8.

The valving member as herein disclosed may comprise a substantially flat circular body plate or disc 12 of metal or other rigid material, having located at opposite ends of a diameter or chord the axially aligned cylindrical shaft sections 14 and 16. The shaft section 14 may be considered a stud shaft or journal adapted to rotate in a bearing located within a valve body. Shaft section 16 likewise is to be supported in a bearing of the valve body, and may be considered the actuating stem of the valving member.

Shaft sections 14 and 16 may be welded, brazed or otherwise fixedly secured to body plate 12 or if desired, they may be formed integrally therewith as by casting, molding, forging or other process. The assembly may be constructed of a corrosion-resistant material, preferably a metal such as stainless steel, brass, bronze or the like. The axes of shaft sections 14 and 16 are disposed in alignment, and may rest in the mean plane of plate12. The journal stud 14 and a portion of stem 16 may be knurled or otherwise roughened as shown, for effecting a bond with a coating material to be applied thereto.

With further reference to FIG. 1, the outer end of stem or shank 16 may carry a suitable head or the like 18 to receive a wrench, handle or other actuating means whereby the valving member may be rotated axially of members 14 and 16, either manually or by power device. Body plate 12 may be provided with a center hole or through aperture 20, and with a circular row of perforations 22 spaced from the rim or perimeter of the plate. In the finished product, the perforations 20 and 22 will be filled with the plastic material which coats the valving member.

Conical hubs 24 and 26 may form the connections between the shaft sections and plate 12, and each hub may include a conical annular bearing surface denoted 28, 28 arranged concentrically with the shaft section axes. The bearing surfaces 28, 28 are adapted to seal against suitable bearing surfaces of a valve body (not shown) to oppose leakage of fluid along shafts 14 and 16; however, details of this are believed unnecessary for a full understanding of the present invention. All sharp edges are to be removed from the perimeter of body plate 12, and such edges may be rounded oh, by preference.

In accordance with the present invention, the valving member is to be coated with a tough corrosion-resistant material having a low coefficient of friction and the qualities of imperviousness, durability and inherent self-lubrication. The coating material may be a moldable plastic of the class of Teflon TFE (tetrafluoroethylene), or other high density polyethylene, polycarbonate, or polypropylene, and including such products as Teflon FEP, Kynar, Kel-F, Penton and the like.

To apply the coating to the valving member, a bi-part metallic mold is provided (FIGS. 3 through 6), having a first part 30 and a second part 32 provided with substantially identical cavities 34 and 36, the cavities each being shaped to the outline of the valving member, with clearance all around to accommodate the plastic material injected for enveloping the valving member. The outline of each mold cavity corresponds substantially to the shape which results from a plane bisecting the thickness of body plate 12 and shafi sections 14, 16, plus the necessary clearance mentioned.

The mold carries a suitable clamp device 38 which grips the shaft head 18 to center the shaft section 16 within the mold cavity while the mold is closed on the valving member, FIG. 3. A mandrel, which may be in the form of a pointed screw 40, may be advanced into the turning center hole 42 in the stud shaft section 14, to center said shaft section 14 within the mold cavity according to FIG. 3. The mandrel 40 may have a screw-threaded connection at 44 with a normally fixed bridge plate 46 that spans the mold parts, said connection at 44 making possible an axial shifting of the mandrel inner end relative to shaft section 14.

Coating plastic indicated at 48, may be introduced as a heated and pressured fluid into the cavity of mold 30, 32, through a cylinder 49 and sprue 50 by means of a plunger 52. The force of the plunger drives the fluid plastic through plate aperture 20, and laterally in all directions over and under the valving member, until all parts of the valving member which are exposed Within the mold cavity are coated with plastic material.

Before the plastic material sets completely, but while it is sufficiently stable to support the valving member against sagging within the mold cavity, an attendant will manipulate the mandrel 40 to retract its inner end from the turning center hole 42, thereby permitting entry of fluid plastic material into said hole. In this way, the terminal end of shaft section 14 is assured a complete cover of coating material, as is plainly indicated upon FIGS. 4, 5 and 6. The drawing views indicate also a complete uninterrupted coating for shaft section 16, body plate 12, and the hubs 24 and 26. It is noted also that the plastic material fills all the plate apertures 20 and 22, FIGS. 2, 6, 8 and 9.

The plastic material may be introduced under high pressure into the heated mold at a temperature approximating 700 F., and until the mold cavity is filled and plastic material begins to exude through a small vent located at 54. As cooling gradually occurs, the plastic material at about 575 F., though still fluid to some extent, acquires a set sufficient to support the flat body plate 12 and stud 14 without the aid of mandrel 40; and at this stage of the process an attendant will retract the mandrel to permit flow of plastic material into the turning center hole 42 of the stud shaft. After cooling of the assembly to about 300 F,, the mold may be parted to release the coated valving member illustrated by FIGS. 2, 7 and 8.

At the time of retracting the mandrel 40, the body plate 12 should be disposed with its plane horizontal so as to offer maximal surface area to the partially set coating material underlying and supporting said plate. This avoids any tendency of the body plate to cleave or shear the partially set material. Alternatively, the mold might be disposed with the rotating axis of the valving member upright, to the same advantage.

The reference numeral 56, FIG. 6, indicates a thermocouple or similar temperature responsive device used in measuring the mold temperature at all stages of the molding or coating procedure.

By preference, though not of necessity, the shaft sections 14 and 16 are knurled or otherwise roughened as in FlGS. 1, 6 and 7, to enhance adherence of the coating material and preclude any tendency thereof to slip either lengthwise or rotationally of the shaft sections. Also, the head end 18 of shaft section 16 may remain uncoated, if desired. With the possible exception of head 18, all metallic surfaces of the valving member are protected fully by the coating of molded plastic material. The coating of molded plastic material is identified by the reference numeral 58. As was previously pointed out, the coating material utilized has a high degree of durability and will effectively protect the valving member and its journals against the destructive action of corrosive liquids and gases when incorporated in a valve body.

What is claimed is:

1. The method of applying a protective coating to a butterfly-type valving member comprising a substantially flat circular body plate having located at opposite ends of a diameter or chord thereof a pair of axially aligned cylindrical shaft sections, one of which sections is a stud shaft having a terminal end provided with a turning center hole, and the other of which sections constitutes an actuating stern having an outer end, said method comprising: placing the valving member in a separable mold having a cavity complementing the contour of the valving member, the cavity having clearance at all points of the valving member disposed therein; mechanically supporting at the turning center hole the terminal end of the stud shaft, and supporting the outer end of the actuating stem, to center and support the valving member in the mold cavity with a substantial uniformity of cavity clearance; injecting into the mold cavity under pressure a heat-fluidified plastic coating material to fill the cavity and flow about the body plate and the shaft sections; reducing the mold temperature to partially set the plastic material to the extent of providing support for the weight of the body plate and the stud shaft; then removing the mechanical support for the terminal end of the stud shafi, to impose the weight thereof upon the partially set plastic material aforesaid while exposing the turning center hole for entry therein of plastic material; continuing the pressure-feeding of heat-softened plastic material into the mold cavity for filling the exposed turning center hole; then further reducing the mold temperature to solidify all of the plastic material within the mold cavity; then finally parting the mold to release the coated valving member.

2. The method as defined by claim 1, wherein the protective coating material is a material of the class of tetrafiuoroethylene or the like.

3. The method as defined by claim 1, wherein the coating material is injected into the mold cavity at a temperature approximating 700 R, which is reduced to about 575 F. at the time of removing the mechanical support for the terminal end of the stud shaft.

4. The method as defined by claim 3, wherein the protective coating material is a material of the class of tetrafiuoroethylene or the like.

5. The method as defined by claim 3, wherein removal of mechanical support from the terminal end of the stud shaft is performed with a plane of the body plate disposed substantially horizontally.

6. The method as defined by claim 5, wherein the protective coating material is a material of the class of tetrafluoroethylene or the like.

7. The method as defined by claim 5, wherein removal of mechanical support from the terminal end of the stud shaft is performed with the axis of the stud shaft disposed substantially vertically.

8. The method as defined by claim 3, wherein removal of mechanical support from the terminal end of the stud shaft is performed with the axis of the stud shaft disposed substantially vertically.

9. The method as defined by claim 1, wherein distribution of heated plastic coating material throughout the mold cavity is facilitated by providing the substantially flat body plate with at least one through perforation which upon release of the valving member from the mold remains filled with solidified coating material.

10. The method as defined by claim 1, wherein removal of mechanical support from the terminal end of the stud shaft is performed with the plane of the body plate disposed substantially horizontally.

11. The method as defined by claim 1, wherein removal of mechanical support from the terminal end of the stud shaft is performed with the axis of the stud shaft disposed substantially vertically.

12. The method as defined by claim 1, wherein an end portion of the actuating stem is disposed exteriorly of the mold cavity and is accordingly not subject to coating.

13. The method as defined by claim 1, wherein the mechanical support at the turning center hold of the stud shaft includes an axially shiftable mandrel having an inner end within the mold cavity to enter and leave said turning center hole depending upon the direction of axial shifting of the man- 5 drel. 

2. The method as defined by claim 1, wherein the protective coating material is a material of the class of tetrafluoroethylene or the like.
 3. The method as defined by claim 1, wherein the coating material is injected into the mold cavity at a temperature approximating 700* F., which is reduced to about 575* F. at the time of removing the mechanical support for the terminal end of the stud shaft.
 4. The method as defined by claim 3, wherein the protective coating material is a material of the class of tetrafluoroethylene or the like.
 5. The method as defined by claim 3, wherein removal of mechanical support from the terminal end of the stud shaft is performed with a plane of the body plate disposed substantially horizontally.
 6. The method as defined by claim 5, wherein the protective coating material is a material of the class of tetrafluoroethylene or the like.
 7. The method as defined by claim 5, wherein removal of mechanical support from the terminal end of the stud shaft is performed with the axis of the stud shaft disposed substantially vertically.
 8. The method as defined by claim 3, wherein removal of mechanical support from the terminal end of the stud shaft is performed with the axis of the stud shaft disposed substantially vertically.
 9. The method as defined by claim 1, wherein distribution of heated plastic coating material throughout the mold cavity is facilitated by providing the substantially flat body plate with at least one through perforation which upon release of the valving member from the mold remains filled with solidified coating material.
 10. The method as defined by claim 1, wherein removal of mechanical support from the terminal end of the stud shaft is performed with the plane of the body plate disposed substantially horizontally.
 11. The method as defined by claim 1, wherein removal of mechanical support from the terminal end of the stud shaft is performed with the axis of the stud shaft disposed substantially vertically.
 12. The method as defined by claim 1, wherein an end portion of the actuating stem is disposed exteriorly of the mold cavity and is accordingly not subject to coating.
 13. The method as defined by claim 1, wherein the mechanical support at the turning center hold of the stud shaft includes an axially shiftable mandrel having an inner end within the mold cavity to enter and leave said turning center hole depending upon the direction of axial shifting of the mandrel. 